
// Copyright (c) 2010 libmv authors.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to
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// furnished to do so, subject to the following conditions:
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// The above copyright notice and this permission notice shall be included in
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// IN THE SOFTWARE.

// Copyright (c) 2012, 2013 Pierre MOULON.

// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.

#ifndef OPENMVG_MULTIVIEW_SOLVER_HOMOGRAPHY_KERNEL_H_
#define OPENMVG_MULTIVIEW_SOLVER_HOMOGRAPHY_KERNEL_H_

#include <vector>

namespace openMVG {
namespace homography {
namespace kernel {

using namespace std;

struct FourPointSolver {
    enum { MINIMUM_SAMPLES = 4 };
    enum { MAX_MODELS = 1 };
    /**
     * Computes the homography that transforms x to y with the Direct Linear
     * Transform (DLT).
     *
     * \param x  A 2xN matrix of column vectors.
     * \param y  A 2xN matrix of column vectors.
     * \param Hs A vector into which the computed homography is stored.
     *
     * The estimated homography should approximately hold the condition y = H x.
     */
    static void Solve(const Mat &x, const Mat &y, vector<Mat3> *Hs);
};

Vec3 EuclideanToHomogeneous(const Vec2 &x);
// Should be distributed as Chi-squared with k = 2.
struct AsymmetricError {
    static double Error(const Mat &H, const Vec2 &x1, const Vec2 &x2) {
        Vec3 x2h_est = H * EuclideanToHomogeneous(x1);
        Vec2 x2_est = x2h_est.head<2>() / x2h_est[2];
        return (x2 - x2_est).squaredNorm();
    }
};
} // namespace kernel
} // namespace homography
} // namespace openMVG

#endif // OPENMVG_MULTIVIEW_SOLVER_HOMOGRAPHY_KERNEL_H_
